Apparatus For Forming Composite Membrane With Porous Coating Layer

ABSTRACT

The present invention discloses a method for forming a composite membrane with a porous coating layer. At first, a filling process is carried out to fill the pores of a porous substrate with a liquid. Next, a raw material is transformed into melt or incomplete melt droplets by a heating source and the droplets are sprayed to the surface of the porous substrate filled with the liquid. The liquid is evaporated by the high temperature droplets and plasma flame to become vapor and the vapor breaks through the droplets to have the droplets sputter into different blocks to thereby form random and dispersed flat particles after cooled. Flat particles are formed and stacked continuously so as to form a composite membrane with a porous coating layer. Moreover, the invention provides an apparatus for forming a composite membrane with a porous coating layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. Ser. No. 12/117,287, filed May 08, 2008 bythe same inventors, and claims priority there from. This divisionalapplication contains rewritten claims to the restricted-out subjectmatter of original claims.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to a method for forming acomposite membrane and an apparatus thereof, and more particularly to amethod for forming a composite membrane with a porous coating layer andan apparatus thereof.

2. Description of the Prior Art

Membrane separation is energy-saving and economical separationtechnique. Thus, the membrane separation process has gradually becomeimportant in chemical industry, water treatment, food processing,biomedical technology, electronic industry, and so forth. In themembrane separation process, the material of membrane can be organic,inorganic, or organic/inorganic hybrid. Since inorganic material has theadvantages of thermal stability, mechanical stability, and chemicalstability, inorganic membrane has been widely applied in separation,either in micro filtration, ultra filtration, gas separation, or even inmembrane reactor.

Inorganic membrane generally can be categorized into two types, densemembrane and porous membrane, according to the morphology of itssurface. Since the porous membrane has higher permeability than thedense one, it has been widely applied in various industries. Besides,the porous membrane has more functionalities than the dense one and canbe applied in gas separation, micro filtration and ultra filtration forsolid-liquid separation, and even nano-filtration.

Among the methods for preparing porous inorganic membrane, methods likesol-gel method, solid particle sintering method, and chemical vapordeposition (CVD), etc., are common ones, but these processes havedisadvantages of complicated processing, time consuming, limitedselection in raw materials to limit the industrial application thereof.Therefore, in order to solve the above-mentioned problems, it isnecessary to develop a new membrane apparatus and process to manufacturea composite membrane with a porous coating layer to reduce manufacturingcost.

SUMMARY OF THE INVENTION

In light of the above background, in order to fulfill the requirementsof the industry, the present invention provides a method for forming acomposite membrane with a porous coating layer and an apparatus thereofso as to solve the above problems in the prior art.

One object of the present invention is to utilize the principle ofliquid vaporization by heat to prepare a porous inorganic membrane. Atfirst, melt droplets are sprayed to the surface of a porous substratefilled with a liquid. The liquid is evaporated by the high temperaturedroplets and plasma flame to become vapor and the vapor breaks throughthe droplets to have the droplets sputter into different blocks tothereby form random and dispersed flat particles after cooled. Flatparticles are formed and stacked continuously so as to form a compositemembrane with a porous coating layer.

Another object of the present invention is to use organic polymericmaterial and/or inorganic material to form an organic/inorganic coatinglayer. On the contrary, the prior techniques such as sol-gel method,solid particle sintering method, and chemical vapor deposition, are notfeasible to prepare organic porous membranes or organic/inorganiccomposite membranes. Therefore, this present invention does have theeconomic advantages for industrial applications.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

What is probed into the invention is a method for forming a compositemembrane with a porous coating layer and an apparatus thereof. Detaildescriptions of the device and steps will be provided in the followingin order to make the invention thoroughly understood. Obviously, theapplication of the invention is not confined to specific detailsfamiliar to those who are skilled in the art. On the other hand, thecommon steps or devices that are known to everyone are not described indetails to avoid unnecessary limits of the invention. Some preferredembodiments of the present invention will now be described in greaterdetail in the following. However, it should be recognized that thepresent invention can be practiced in a wide range of other embodimentsbesides those explicitly described, that is, this invention can also beapplied extensively to other embodiments, and the scope of the presentinvention is expressly not limited except as specified in theaccompanying claims.

In a first embodiment of the present invention, a method for forming acomposite membrane with a porous coating layer is provided. At first, aporous substrate is provided. The porous substrate is ceramic ormetallic porous substrate with a pore diameter less than or equal to 100μm. A filling process to fill the pores of the porous substrate with aliquid is carried out. The liquid can be water, alcohol, ketone, orcombination thereof. The filling process can be pressurized typefilling, showering type filling, vacuum suction type filling, anddipping type filling. Following that, a melting process is performed totransform a raw material into melt or incomplete melt droplets by a heatsource, such as flame, arc, or plasma. Then, spraying these droplets tothe surface of the porous substrate filled with the liquid is performedto complete a spraying process. In the spraying process, these dropletsimpact the surface of the porous substrate and diffuse towardssurroundings after colliding to form planarized droplets. Theevaporation of the liquid is induced by these high temperature dropletsand plasma flame (the temperature higher than the boiling point of theliquid) and then the liquid becomes vapor. The vapor breaks through thethinner portion of the planarized droplets to have the droplets sputterinto different blocks to thereby form random and dispersed flatparticles after cooled. By repeatedly performing the spraying process,flat particles are formed and stacked continuously so as to form acomposite membrane with a porous coating layer. After the process offorming the composite membrane with a porous coating layer, the filling,melting, and spraying process can be performed to increase the thicknessof the coating layer. In addition, the inorganic material comprises onematerial selected from the group consisting of the following or anycombination thereof: alkali metal, alkaline earth metal, mixture ofalkali and alkaline earth metal silicates, aluminum silicates, zirconiumsilicates, hydrated silicates, aluminates, oxides, nitrides,oxynitrides, carbides, oxycarbides, borates, titanates, phosphates,halides, and derivatives thereof. In a preferred example of thisembodiment, the melting process and spraying process can be combinedinto a thermal spraying process or an atmospheric plasma sprayingprocess.

In a second embodiment of the present invention, an apparatus forforming a composite membrane with a porous coating layer is disclosed.The apparatus comprises a heat source generating device, a raw materialtransporting device, a filling device, and spraying device. The rawmaterial transporting device transports a raw material to the heatsource generating device and the raw material is transformed into meltor incomplete melt droplets by a heat source, such as flame, arc, orplasma. Besides, the filling device is to fill the pores of a poroussubstrate with a liquid and the porous substrate is of ceramics ormetal. The liquid can be water, alcohol, ketone, or mixture thereof. Thespraying device sprays the droplets to the surface of the poroussubstrate filled with the liquid. The liquid is evaporated by the hightemperature droplets and plasma flame (the temperature higher than theboiling point of the liquid) to become vapor and the vapor breaksthrough the droplets to have the droplets sputter into different blocksto thereby form random and dispersed flat particles after cooled. Flatparticles are formed and stacked continuously so as to form a compositemembrane with a porous coating layer. The filling device can be apressurized type filling device, showering type filling device, vacuumsuction type filling device, and dipping type filling device. Inaddition, the heat source generating device adjusts electric powersupply and the temperature of a heat source according to a first signal,the raw material transporting device adjusts the speed of rawtransportation according to a second signal, and the spraying deviceadjusts the speed of spraying according to a third signal. Besides, thefirst, second and third signals are generated by a control device.

In a third embodiment of the present invention, an apparatus used in anatmospheric plasma spraying process for forming a composite membranewith a porous coating layer is disclosed. The apparatus comprises apower generator, a high frequency generator, a plasma gun, a powderfeeder, and a filling device. The high frequency generator uses suppliedelectric power to generate high frequency spark and ignite an arc. Thearc energy is used by the plasma gun to ionized inert gas and togenerate a plasma jet flow in the plasma gun. The powder feeder feeds apowder into the plasma gun and uses the temperature of the plasma jetflow to transform the powder into melt or incomplete melt droplets. Thefilling device is to fill the pores of a porous substrate with a liquid.The plasma jet flow sprays the droplets to the surface of the poroussubstrate filled with the liquid. The liquid is evaporated by the hightemperature droplets and plasma flame (the temperature higher than theboiling point of the liquid) to become vapor and the vapor breaksthrough the droplets to have the droplets sputter into different blocksto thereby form random and dispersed flat particles after cooled. Flatparticles are formed and stacked continuously so as to form a compositemembrane with a porous coating layer. The material of the poroussubstrate, the liquid, and the filling device are in the same manner asthose in the second embodiment. In addition, the power generator adjustselectric power supply according to a first signal, the high frequencygenerator adjusts start ignition according to a second signal, theplasma gun adjusts the speed of spraying according to a third signal,the powder feeder adjusts the speed of transporting powder according toa fourth signal, and besides the first, second, third, and fourthsignals are generated by a control device.

The thermal spraying method is a new method for preparing membranes,generally for preparing dense inorganic membranes. The commonatmospheric plasma spraying technique is a spraying process underatmosphere and the porosity of the thus formed coating layer is high.Therefore, the density of membrane by atmospheric plasma spraying is nothigher enough for the users in applying protection coating byatmospheric plasma spraying. Thus, there are various processes developedin atmospheric plasma spraying technique. For a long time, such acharacteristic, the coating layer with high porosity fabricated byatmospheric plasma spraying, that is thought to be failure, has not beenapplied in the method for preparing porous membranes. The inventionconquers the technical bias by those who are skilled in the art and usessuch discarded technique and improves it to achieve high porosity. Thus,the invention can not be easily achieved.

Obviously many modifications and variations are possible in light of theabove teachings. It is therefore to be understood that within the scopeof the appended claims the present invention can be practiced otherwisethan as specifically described herein. Although specific embodimentshave been illustrated and described herein, it is obvious to thoseskilled in the art that many modifications of the present invention maybe made without departing from what is intended to be limited solely bythe appended claims.

1. An apparatus for forming a composite membrane with a porous coatinglayer, comprising: a heat source generating device; a raw materialtransporting device to transport a raw material to said heat sourcegenerating device wherein said raw material is transformed into melt orincomplete melt droplets by a heat source; a filling device to fill thepores of a porous substrate with a liquid; and a spraying device tospray said droplets to the surface of said porous substrate wherein saidliquid is evaporated by said high temperature droplets and plasma flameto become vapor, the vapor breaks through said droplets to have saiddroplets sputter into different blocks to thereby form random anddispersed flat particles after cooled, and flat particles are formed andstacked continuously so as to form a composite membrane with a porouscoating layer.
 2. The apparatus according to claim 1, wherein said heatsource generating device adjusts electric power supply and thetemperature of a heat source according to a first signal, said rawmaterial transporting device adjusts the speed of raw transportationaccording to a second signal, said spraying device adjusts the speed ofspraying according to a third signal, and besides said first signal ,said second signal and said third signal are generated by a controldevice.
 3. The apparatus according to claim 1, wherein said heatingsource generated by said heat source generating device comprises onesource selected from the group consisting of the following or anycombination thereof: flame, arc, or plasma.
 4. The apparatus accordingto claim 1, wherein said porous substrate is of ceramics or metal. 5.The apparatus according to claim 1, wherein said liquid comprises onesubstance selected from the group consisting of the following or anycombination thereof: water, alcohol, or ketone.
 6. The apparatusaccording to claim 1, wherein said filling device comprises one deviceselected from the group consisting of the following: pressurized typefilling device, showering type filling device, vacuum suction typefilling device, and dipping type filling device.
 7. The apparatusaccording to claim 1, wherein the temperature of said droplets is higherthan the boiling point of said liquid.
 8. An apparatus used in anatmospheric plasma spraying process for forming a composite membranewith a porous coating layer, comprising: a power generator for supplyingelectric power; a high frequency generator using said electric power togenerate high frequency spark and ignite an arc; a plasma gun usinginert gas ionized by the energy of said arc to generate a plasma jetflow therein; a powder feeder for feeding a powder into said plasma gunwherein said powder is transformed into melt or incomplete melt dropletsvia the temperature of said plasma jet flow; and a filling device forfilling the pores of a porous substrate with a liquid wherein saidplasma jet flow sprays said droplets to the surface of said poroussubstrate filled with said liquid, said liquid is evaporated by saidhigh temperature droplets and plasma flame to become vapor, the vaporbreaks through said droplets to have said droplets sputter intodifferent blocks to thereby form random and dispersed flat particlesafter cooled, and flat particles are formed and stacked continuously soas to form a composite membrane with a porous coating layer.
 9. Theapparatus according to claim 8, wherein said power generator adjustselectric power supply according to a first signal, said high frequencygenerator adjusts start ignition according to a second signal, saidplasma gun adjusts the speed of spraying according to a third signal,said powder feeder adjusts the speed of transporting powder according toa fourth signal, and besides said first, second, third, and fourthsignals are generated by a control device.
 10. The apparatus accordingto claim 8, wherein said porous substrate is of ceramics or metal. 11.The apparatus according to claim 8, wherein said liquid comprises onesubstance selected from the group consisting of the following or anycombination thereof: water, alcohol, or ketone.
 12. The apparatusaccording to claim 8, wherein the temperature of said droplets is higherthan the boiling point of said liquid.
 13. The apparatus according toclaim 8, wherein said filling device comprises one device selected fromthe group consisting of the following: pressurized type filling device,showering type filling device, vacuum suction type filling device, anddipping type filling device.